Renin Activity, Plasma

Test ID: 

704096

CPT code:

84244

Synonyms:

Plasma Renin Activity (PRA)
PRA

Clinical Use:

Measurement of renin activity is useful in the differential diagnosis of individuals with hypertension. Renin levels will be elevated in patients with hypertension due to renal artery stenosis (ie, renovascular hypertension). Measurement of renin activity can also be useful in the diagnosis of primary aldosteronism. Patients with secondary aldosteronism tend to have low renin levels. Renin can also be used to assess the adequacy of steroid substitution in patients with adrenal insufficiency. Renin activity will be normal in patients with adequate supplementation and will be elevated when steroid substitution is inadequate.

Specimen Type:

Plasma, frozen

Requested Volume: 

1 mL

Minimum Volume: 

0.8 mL (Note: This volume does not allow for repeat testing.)

Container Type: 

In order to facilitate interpretation of test results, the patient should be taken off medications for at least three weeks prior to sample collection. Dietary sodium levels during the period prior to testing can affect renin levels. Sodium restriction tends to cause an increase in renin activity, while supplementation can result in lower values. A 24-hour urine sodium determination from a sample collected on the day before a renin test can be used to assess sodium intake. Expected renin activity levels for various levels of urinary sodium excretion are provided. Renin activity determination without the concurrent urine sodium measurement can still provide useful information if the clinician verifies that the patient has been on a normal sodium diet.  Since patient posture prior to collection affects renin levels, it is recommended that the patient be ambulatory for at least 30 minutes before blood collection.1 If inpatients are physically able, they should be asked to ambulate for 30 minutes before blood is drawn for renin activity. Reference intervals are provided for patients who have ambulated for at least 30 minutes prior to collection (upright patients). Reference intervals are also provided for patients on a normal sodium diet who are unable to ambulate (supine patients).

Patient Preparation: 

In order to facilitate interpretation of test results, the patient should be taken off medications for at least three weeks prior to sample collection. Dietary sodium levels during the period prior to testing can affect renin levels. Sodium restriction tends to cause an increase in renin activity, while supplementation can result in lower values. A 24-hour urine sodium determination from a sample collected on the day before a renin test can be used to assess sodium intake. Expected renin activity levels for various levels of urinary sodium excretion are provided. Renin activity determination without the concurrent urine sodium measurement can still provide useful information if the clinician verifies that the patient has been on a normal sodium diet.  Since patient posture prior to collection affects renin levels, it is recommended that the patient be ambulatory for at least 30 minutes before blood collection.1 If inpatients are physically able, they should be asked to ambulate for 30 minutes before blood is drawn for renin activity. Reference intervals are provided for patients who have ambulated for at least 30 minutes prior to collection (upright patients). Reference intervals are also provided for patients on a normal sodium diet who are unable to ambulate (supine patients).

Collection:

Draw blood into an EDTA tube. Keep tube at room temperature. Centrifuge at room temperature.  Transfer the plasma into a LabCorp PP transpak frozen purple tube with screw cap . Freeze immediately and maintain frozen until tested. It is critical that the plasma be transferred and frozen as quickly as possible to prevent cryoactivation of protein to renin (which results in falsely elevated renin levels). To avoid delays in turnaround time when requesting multiple tests on frozen samples, please submit separate frozen specimens for each test requested.

Storage Instructions:

Freeze

Stability Requirements:

Temperature

Period

Room temperature

Unstable

Refrigerated

Unstable

Frozen

14 days

Freeze/thaw cycles

Stable x1

Rejection Criteria

Nonfrozen sample received; nonseparated sample received; non-EDTA plasma specimen; gross hemolysis or lipemia

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